Magic: The Gathering Comprehensive Rules Changes - Core Set - Ninth Edition to Ravnica: City of Guilds

Old rule (Core Set - Ninth Edition)	New rule (Ravnica: City of Guilds)
408.1d. [Click to view all changes.]
408.1d. A player may play a spell or activated ability only when he or she has priority. Spells other than instants can be played only during a player's main phase, when that player has priority and the stack is empty.	408.1d. A player may play an instant spell or an activated ability any time he or she has priority. Spells other than instants may be played during a player's main phase, when that player has priority and the stack is empty.

Old rule (Core Set - Ninth Edition)

New rule (Ravnica: City of Guilds)

408.1d.

A player may play a spell or activated ability only when he or she has priority. Spells other than instants can be played only during a player's main phase, when that player has priority and the stack is empty.

408.1d.

A player may play an instant spell or an activated ability any time he or she has priority. Spells other than instants may be played during a player's main phase, when that player has priority and the stack is empty.